Speech research from 1948 to 1974 framed spoken communication as a perceptually anchored coding problem, guiding analysis, synthesis, and evaluation of intelligibility through perceptual cues. Phonetic and formant analysis became the core toolkit, enabling automatic formant extraction, onset-time discrimination, and phoneme boundary detection within processing pipelines. Neural and brain-level studies linked speech processing to cognitive substrates and hemispheric specialization, while production–perception integration highlighted the interactive nature of articulation and linguistic structure. Early computational work framed automatic recognition and analysis-by-synthesis as foundational approaches for speech technology. Historical Significance: The period produced foundational articulatory–acoustic models connecting vocal tract shaping to acoustic output, underpinning formant transitions and coarticulation; impetus for later production research, speech synthesis, and coding. Foundational perception experiments clarified cue integration and the role of audition in recognition, influencing robust ASR and auditory scene analysis. The Perception of the Speech Code introduced invariant cues enabling phonetic decoding, shaping cognitive models and resilient recognition. Speech Analysis Synthesis and Perception demonstrated the perceptual validity of vocoder-like parameterization, foreshadowing advances in coding and synthesis. The Aeroacoustic general theory on sound generation provided a baseline for articulatory phonetics and early production models.